The speed of change of production requirement for a unit producing carbon monoxide and hydrogen, in connection with a synthesis gas generation unit, a CO2 removal unit and a cold box, is highly dependent on the time of reaction of the cold box.
In a process as described in EP-A-0359629, the acceptable variations of the feed stream at the entrance of the cooling system upstream of the cryogenic separation are very limited. If the changes in feed flow are excessive, the cryogenic separation does not perform correctly and so the speed of feed change is limited to changes of 0.5% of the nominal flow per minute.
Since the synthesis gas generator can react more quickly than the cryogenic separation to changes in feed flow, this means that the cryogenic separation determines the maximum flowrate change.
It has been proposed to use a storage tank containing liquid carbon monoxide to improve the speed of variation of feed flow to produce carbon monoxide. When the demand for carbon monoxide increases quickly, the storage tank is emptied and the carbon monoxide is vaporized in an external vaporizer. This solution does not provide for a fast increase in supply of hydrogen.
Furthermore the storage of large amounts of liquid carbon monoxide presents a security hazard.